Method, System, Mobile Communication Terminal and a Node Adapted for End-to-End Quality Access Selection of an Access Network

ABSTRACT

In a method of selecting an access network from among one or more access networks capable of providing service to a mobile communication terminal, measuring (S 1 ), for at least two access networks, an end-to-end quality through the whole communication path between the terminal and a destination node, and selecting (S 2 ) at least one access based on said measured end-to-end quality.

TECHNICAL FIELD

The present invention relates to multi-radio access systems in general,specifically to a method and an arrangement for access selection in suchsystems.

BACKGROUND

Many mobile communication stations, such as cellular phones, cordlessphones, portable computers, digital assistants, pagers, and the like,now have the capability to access more than one access network. Theseaccess networks may include cellular networks such as Global System forMobile Communications (GSM) and Wideband Code Division Multiple Access(WCDMA), direct wireless networks such as Bluetooth and Wireless LocalArea Networks (WLAN), satellite networks, and the like. For example,some mobile communication stations can be used as both a cellular phoneunder the GSM specification or as a cordless phone under the DigitalEuropean Cordless Telephone (DECT) specification. An application in themobile communication station may then select any of the available accessnetworks to begin communicating with remote applications.

Each access network may provide a number of different services andfeatures therein such as high-speed access, text messaging, callforwarding, and other similar features and services. The mechanisms foraccessing these access networks may include radio frequency connections,infrared connections, modem connections, LAN connections, and othersimilar connections.

Several multi-access scenarios will exist in the near future, forexample CDMA/WLAN. In many cases, more than one of the availableaccesses can carry the same end-user service. For example, best effortpacket data can be carried by both CDMA and WLAN. Consequently, at somepoint in time, a selection of which access to use must be done by theterminal or for the terminal.

In the prior art, it has been observed that the accesses are selectedbased on the quality available on the radio access, in [1] selection isbased on the quality for a service. However, the radio link is notalways the bottleneck for the access.

Accordingly, it is desirable to be able to provide a convenient way toselect an optimal access network.

SUMMARY

An object of the present invention is to provide an improved accessselection method in a multi-access system.

Another object is to provide a method of selecting an access based on anend-to-end quality of an access.

A further object is to provide a method for access selection based on ameasured end-to-end quality for the whole communication path between aterminal and a destination node.

This object is achieved in accordance with the attached claims.

Briefly, the present invention comprises measuring an end-to-end qualityfor a plurality of available radio accesses and selecting at least oneaccess based on the measured quality.

The access selection is based on end-to-end measurements through thewhole communication path. The delay and/or bandwidth can for example bemeasured for all accesses to select among by transmittingacknowledgeable measuring packets with equal or different packet-size.

Further, the invention comprises an arrangement and a system enablingaccess selection based on a measured end-to-end quality between aterminal and a destination node.

Some of the advantages of the present invention are:

-   -   End2end best quality access selection for any type of network.    -   Terminal based access selection that takes into account load and        other limiting factors in any link in the communication path.    -   Multi-operator access selection without any coordination between        operators.    -   No impact on infrastructure.    -   Concurrent use of multiple access paths improving the maximum        end2end quality.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further objects and advantages thereof, maybest be understood by making reference to the following descriptiontaken together with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a multi-access system;

FIG. 2 is another schematic illustration of a multi-access system;

FIG. 3 illustrates an embodiment according to the invention;

FIG. 4 is a schematic flow diagram of an embodiment according to theinvention,

FIG. 5 illustrates an embodiment of an arrangement according to theinvention.

DETAILED DESCRIPTION

The access selections described in [1] only takes the quality of theradio link into account. Since the radio path is only one link in achain of communication links forming the path for the end-to-endservice, this is a very limited approach. Even though the radio linkoften is the limiting link, it is not always the case. In a multi-accessscenario, the core network is typically not uniform and thecommunication path between a terminal and a server can differ completelybetween two radio accesses.

FIG. 1 shows a general multi-access system in which the invention can beimplemented. It comprises at least one terminal that is able tocommunicate or utilize the services of a plurality of available accessnetworks. In the illustration, the different accesses are exemplifiedwith GPRS, WLAN and WCDMA. However, other types of access networks arealso possible.

In FIG. 2 another example of such a multi-access network is shown, inthis case with a 3GPP based core network. Loose inter-working is assumedbetween WLAN and UMTS, i.e. only subscriber handling and securityfunctions are reused from UMTS for the WLAN access and the user planesfor WLAN and UMTS are completely separated

In such networks, there are a number of links that for different reasonscan be the bottleneck for the end-to-end throughput and quality. Thesolution described in the prior art assume, as stated earlier, that theradio link always is this bottleneck.

However, as identified by the inventors, for access over WLAN the firstwired link from the access point (AP) is often the limiting link in thecommunication path, e.g. between the AP and the L2/L3 switch in FIG. 1.This is typically a T1 with 1.5 Mbps in US and Canada, a J1 with 1.5Mbps in Japan or an E1 with 2 Mbps in Europe, sometimes it can even be aDSL with 0.5 Mbps or less. This wired link will then limit the qualityfor WLAN communication since the WLAN radio often has a higherthroughput, up to 7 Mbps with 802.11b and 26 Mbps with 802.11a/g.

Similarly, other links in the network can also be limiting and may varyover time due to different reasons such as varying load.

FIG. 2 further illustrates a scenario where the user plane for WLAN andUMTS/WCDMA is completely separated although one operator controls allaccesses and has the possibility to perform network assisted or networkcontrolled access selection. In [2] an even less coordinated network isdescribed; namely so called terminal control without any networkassistance. In such scenarios, a network controlled selectionalternative is complicated.

According to the invention, a basic solution to find the best qualityaccess is to measure the end-to-end quality through all candidateaccesses to select among between a terminal and a destination node, notonly the quality for the radio link. Subsequently, the measured resultsare compared and that access or those accesses that give the bestend-to-end quality between the terminal and the destination node areselected.

The destination node can be an actual destination node such as anothermobile terminal, or other device which the terminal can communicatewith. Alternatively, the destination node can be an intermediated nodethat is common for some or all available accesses, such as a router orother service node

The term end-to-end quality typically refers to a user perceivedquality, not the overall quality for the system.

FIG. 3 illustrates a scenario, in which the invention can beimplemented, comprising a mobile communication terminal 10 requiringservice from a destination node 30, and which terminal 10 has the optionof selecting between the two access networks 20. In the embodiment, thetwo accesses are WLAN and WCDMA. However, the invention is equallyapplicable to any combination of different networks, operators or accesstechnologies, such as WLAN, CDMA, GPRS etc. Also, the invention isapplicable to a situation where the terminal has to choose among morethan two available accesses.

FIG. 4 illustrates a general method for access selection according tothe invention. Assuming that there are a plurality of availableaccesses, these can be access points or base stations within one accessnetwork, or different access networks, or some other configuration.

Initially, in step S1, the end-to-end quality for each available accessis measured for the whole communication path between a terminal and thedestination node. The destination node can be an actual finaldestination node or an intermediate common node in the system.

The measuring step S1, according to an embodiment of the invention,comprises transmitting an acknowledgeable measuring packet from theterminal to the destination node. Upon receiving an acknowledgement, theend-to-end quality can be determined.

According to another embodiment, the measuring step S1 comprisestransmitting an acknowledgeable measuring packet from an intermediatenode to the terminal. Subsequently, the measurements can be signaled tothe terminal.

The intermediate node can comprise a router or some other node in thesystem, which is utilized by a plurality of accesses.

The acknowledgeable measuring packet, according to a specificembodiment, can be a so called ping-probing packet [3] or a payloadpacket, or some other acknowledgeable predefined packet.

Finally, the measurements are compared and the access or those accessesthat give the best end-to-end quality for the terminal is selected, instep S2, based on the measurements. For some cases it is quite possibleto knowingly select an access that dose not provide the best quality. Apotential scenario is that the cost for accessing the best qualityaccess is too high, thereby preventing selection of the best access.

According to yet another embodiment, both the measuring step S1 and theselection step S2 can be performed at an intermediate node. When a bestaccess is selected, the terminal is then informed of the selection andordered to utilize the selected access.

In a situation where two terminals communicate, the question is whichterminal that should perform the access selection. According to oneembodiment of the present invention, it is quite possible to let bothterminals select its best access to a first common node between theterminals. In that case each terminal performs end-to-end measurementsto the common node and selects the best access. It is equally possiblefor the common node to perform the measurements to each terminal andinform the terminals about the best access for their respectivecommunication path.

The end-to-end quality for a communication path can typically bemeasured as a function of at least delay or bandwidth, or a combinationthereof. This can be measured by transmitting acknowledgeable measuringpackets with different packet sizes towards the destination IP-addressor node. The probing can be done prior the session. It can also be doneperiodically during the session to make a change of access.

Another alternative probing method is to base the probing on some typeof triggers, such as a predetermined lowest/highest quality threshold.

According to another embodiment the end-to-end quality is measured as afunction of packet error rate. In that case, the measurements areperformed by transmitting multiple probing packets or acknowledgeableprobing packets with equal or different packet-size to each availableaccess network.

The measuring packets can be so called ping-probes, but not necessarilyso. Basically, any acknowledgeable data packet with a predetermined sizecan be utilized. Even part of the actual data to be transmitted can beused. It is also possible, for some cases, to transmit some other typeof payload packet.

According to another embodiment of the present invention, if theterminal is assigned one IP-address per access (multi-homing), a softselection can be applied. All accesses to select among are loaded with afraction of the load in order to measure the end-to-end quality.HTTP-sessions are suitable for this solution since they can consist of anumber of TCP-flows. Then the best access is selected for most of theflows while the other accesses are just probed with one flow each. Ormore advanced, load all accesses to increase the maximum possibleend-to-end throughput. The load can be balanced or divided between Naccesses according to:

$L_{n} = {\frac{1}{D_{n} \cdot {\sum\limits_{i = 1}^{N}\frac{1}{D_{i}}}} \cdot L_{tot}}$

where L_(tot) is the total load, L_(n) is the load or utilization foraccess n, D_(n) is the normalized round trip time in s/kbit for accessn, and N is the number of accesses.

A numerical example of dividing the load or utilization from a terminalon more than one available access will now be described. According tothe example, two accesses are available, one with 2 Mbps throughput andthe other with 1 Mbps, that shall be loaded with a 60 kbps service. A 1kbyte packet is sent on the first access resulting in a 4 ms delay and a1 kbyte packet on the second access results in a 8 ms delay. Thenormalized delays are; D₁=0.004 s/kbit, D₂=0.008 s/kbit, resulting inL₁=40 kbps and L₂=20 kbps. Consequently, the data to be transmitted isdivided on the two accesses according to L₁ and L₂.

In FIG. 5, a general embodiment of an arrangement such as a userterminal 10 according to the invention is illustrated. The terminal 10comprises an input/output unit 11, a unit 12 enabling end-to-end qualitymeasurements, and an access selection unit 13.

According to the embodiment, the measuring unit 12 is adapted to measurethe end-to-end quality between the terminal and a destination node. Thedestination node can comprise an actual destination node, or anintermediate node that is common for all available accesses. The unit 12is further adapted to perform the measurements by transmittingacknowledgeable measuring packets to the destination node, and uponreception of the acknowledgement determining the end-to-end quality forthe access. The measurements can comprise delay and/or bandwidth and/orsome other parameter.

According to another embodiment, the unit 12 is adapted to transmitmultiple measuring packets with different packet size, and therebyenabling measuring packet error rate.

According to yet another embodiment, the end-to-end quality determiningunit 12 is configured to receive measurements from another node.Alternatively, the unit 12 is further adapted to receive information ofa best access, which is selected at some other node in the system,possibly a router.

The access selection unit 13 is adapted to select at least one access 20based on the measured end-to-end quality for each available access fromthe terminal 10 to a destination node.

Additionally the invention comprises a node in a multi-accesstelecommunication system. The node comprises, a unit 12 enablingend-to-end quality measurements, and an optional access selection unit13.

According to the embodiment, the measuring unit 12 is adapted to measurethe end-to-end quality between a terminal and a destination node. Theunit 12 is further adapted to perform the measurements by transmittingacknowledgeable measuring packets to the terminal, and upon reception ofthe acknowledgement determining the end-to-end quality for the access.

If the optional access selection unit 13 is included in the node, it isfurther adapted to signal or report the selected access to the terminal,thereby informing the terminal which access to use for a best end-to-endquality.

According to the invention, a system enabling access selection based onend-to-end quality measurements is provided. Accordingly, the systemcomprises a measuring unit 12 configured for measuring, for each accessnetwork, an end-to-end quality through a whole communication path from aterminal 10 to a destination node 30, and an access selection unit 13adapted to select at least one access based on the measured quality.

The measuring unit 12 of the system is typically located in a mobilecommunication terminal or user equipment, but it is also possible tolocate the measuring unit 12 in some other node and signal themeasurements or accesses selected based on the measurements to theterminal.

It will be understood by those skilled in the art that variousmodifications and changes may be made to the present invention withoutdeparture from the scope thereof, which is defined by the appendedclaims.

REFERENCES

-   [1] Patent: “Method of Multi-Service Allocation in Multi-Access    Systems”, WO 03/088686-   [2] P. Magnusson et al, “Radio Resource Management Distribution in a    Beyond 3G Multi-Radio Access Architecture”, submission to Globecom    2004.-   [3] www.ping127001.com/pingpage.htm

1-26. (canceled)
 27. A method of selecting an access network from amongone or more radio access networks, belonging to one or several differentoperators, where each said access network is capable of providingservice to a mobile communication station, the method comprising:measuring, for at least two access networks, an end-to-end qualitythrough the whole communication path, each said communication pathincluding both radio links and wired links between the terminal and adestination node, and selecting at least one access based on saidmeasured end-to-end quality.
 28. The method according to claim 27,wherein said measuring step is performed at the terminal.
 29. The methodaccording to claim 27, wherein said measuring step is performed at anintermediate node.
 30. The method according to claim 27, wherein saidmeasuring step comprising transmitting at least one acknowledgeablemeasuring packet through each access between the terminal and thedestination node.
 31. The method according to claim 27, furthercomprising measuring said end-to-end quality as a function of at least adelay for each access.
 32. The method according to claim 27, furthercomprising measuring said end-to-end quality as a function of at leastbandwidth for each access.
 33. The method according to claim 30, whereinsaid measuring step comprising transmitting multiple acknowledgeablemeasuring packets through each access between the terminal and thedestination node.
 34. The method according to claim 30, furthercomprising transmitting acknowledgeable measuring packets with differentsizes.
 35. The method according to claim 33, further comprisingmeasuring said end-to-end quality as a function of a packet error ratefor each access.
 36. The method according to claim 30, wherein saidacknowledgeable measuring packet is a ping packet.
 37. The methodaccording to claim 30, wherein said acknowledgeable measuring packet isa payload packet.
 38. The method according to claim 27, furthercomprising: selecting more than one access, and transmitting fractionsof the data to be transmitted on each selected access, based on themeasured end-to-end quality for each access.
 39. The method according toclaim 34, further comprising transmitting fractions of the databasically according to:$L_{n} = {\frac{1}{D_{n} \cdot {\sum\limits_{i = 1}^{N}\frac{1}{D_{i}}}} \cdot L_{tot}}$where L_(tot) is the total load, L_(n) is the load or utilization foraccess n, D_(n) is the normalized round trip time in s/kbit for accessn, and N is the number of accesses selected.
 40. A system enablingselection of an access network from among one or more radio accessnetworks belonging to one or several different operators, where eachsaid access is capable of providing service to a mobile communicationstation, the system comprising: means for measuring, for each accessnetwork, an end-to-end quality through the whole communication path,each said communication path including both radio links and wired linksbetween the terminal and a destination node, and means for selecting atleast one access based on said measured end-to-end quality.
 41. Thesystem according to claim 40, wherein said measuring means are locatedin the terminal.
 42. The system according to claim 40, wherein saidmeasuring means are located in an intermediate node,
 43. The systemaccording to claim 42, wherein said measuring means are further adaptedto transmit the measurements results to the terminal.
 44. The systemaccording to claim 42, characterized in that said selecting means arelocated in one of the intermediate node, the terminal or another node.45. The system according to claim 40, wherein said measuring means areconfigured to transmit at least one acknowledgeable measuring packetthrough each access between the terminal and the destination node. 46.The system according to claim 40, wherein said measuring means areconfigured to measure said end-to-end quality as a function of at leastdelay and/or bandwidth for each access.
 47. The system according toclaim 40, wherein said measuring means are configured to transmitmultiple acknowledgeable measuring packets through each access betweenthe terminal and the destination node.
 48. The system according to claim47, wherein said measuring means are configured to measure saidend-to-end quality as a function of a packet error rate for each access.49. The system according to claim 40, wherein said selecting means areconfigured to select more than one access, and to transmit fractions ofdata to be transmitted on each selected access, based on the measuredend-to-end quality for each access.
 50. A node in a multi-radio accesstelecommunication system, further comprising: means for measuring, foreach access network, an end-to-end quality through the wholecommunication path, each said communication path including both radiolink and wired links between a terminal and a destination node, andmeans for selecting at least one access for the terminal based on saidmeasured end-to-end quality.
 51. The node according to claim 50, whereinsaid selecting means are further adapted to report said selected atleast one access to the terminal.
 52. A mobile communication terminalcapable of using one or more access networks belonging to one or severaldifferent operators in a multi-radio access system, the terminalcomprising: means for measuring, for each access network, an end-to-endquality through the whole communication path, each said communicationpath including both radio link and wired links between the terminal anda destination node, and means for selecting at least one access based onsaid measured end-to-end quality.